In the mining industry, in fields such as rock quarry excavation and the like, the desired mineral often lies below ground level. Explosive charges are employed to break up the mineral into small pieces so that it may easily be gathered. In this process, typically a plurality of blast holes arranging in diameter from a few inches to well over a foot are drilled in the earth and explosive charges are inserted in the blast hole, together with primers to detonate the charges.
The most commonly used explosive for such blast holes is ammonium nitrate which typically contains a small amount of fuel oil, i.e., about 6%. In the industry this explosive which is in the form of a loose powder bulk material is referred to as "ANFO." When ANFO is wetted over 11%, it will not explode; at water levels less than 11%, the explosive quality of the material and the force of the explosive blast is not nearly as satisfactory as when the blast hole is dry.
Of course, in areas which have high ground water content, it often happens that a blast hole after drilling will fill with water. Of course, if the blast hole is filled with water, this will result in a wetting of the ANFO charge coupled with an attendant decrease or lessening in the effectiveness of the blast. As a result a first step involves dewatering the blast hole, and this is done prior to lining of the blast hole as explained hereinafter.
Efforts to solve this problem in the prior art have resulted in the utilization of blast hole liners. This invention relates to an improved blast hole liner and to an apparatus for conveniently dispensing the improved blast hole liner.
As one can well imagine, it is often very difficult to quickly and efficiently place a moisture-proof blast hole liner in a blast hole of reasonably small diameter. Many potential interfering possibilities can occur which may necessitate long waiting times between actual drilling of a blast hole and use of the blast hole. Of course, such long time lapses are uneconomical, inefficient and wasteful. As an example, flat blast hole liner sleeves of the construction shown in Kallister et al, U.S. Pat. No. 3,706,727 are often unsatisfactory and nonusable because flat blast hole liners have a propensity to develop air pockets therein during the pouring of ANFO in the blast hole liner with the result being that an ANFO does not easily fall to the bottom of the liner. Such air pockets once formed eventually will dissipate because of the bulk form of the ANFO but this often will take 15 to 30 minutes which represents an intolerable delay. In addition, blast hole liners having flat edges forming a longitudinal sleeve seam are unsuitable since the flat sleeve edges often press against the blast hole walls which may be wet, and may adhere to the blast hole walls and prevent the effective lowering of the liner to the bottom of the blast hole. In addition, where the blast hole walls are somewhat uneven, blast hole liners of the flat design having longitudinal seams often rub against the blast hole wall and can snag on ragged edges of the wall causing leakage in the liner.
In addition to a preferred structure for a blast hole liner, applicant's invention also involves the development of a convenient dispensing stand for a blast hole liner. This stand is portable, light weight and convenient for usage under a variety of circumstances and conditions. In addition, this stand allows for a significant decrease in time for placing a blast hole liner in a blast hole and filling the liner with an explosive charge of ANFO or the like.
Accordingly, one object of this invention is to provide an improved blast hole liner.
Another object of this invention is to provide an improved blast hole liner which if free from longitudinal seams and/or edges extending along the sleeve.
Yet another object of this invention is to provide a blast hole liner which can quickly and easily be manufactured from a roll of liner sleeving.
Yet another object of this invention is to provide a blast hole liner which is of a construction which prevents air pockets from forming during the loading of bulk explosive into the blast hole liner.
Yet another object of this invention is to provide a blast hole liner which is of a construction which will prevent the blast hole liner from adhering to the wet walls of a blast hole and which will minimize the possibility of the blast hole liner from snagging on the ragged edges of the blast hole walls.
Yet another object of this invention is to provide a portable blast hole liner sleeving stand.
Yet another object of this invention is to provide a blast hole sleeving stand which is light weight, easy to use, and which will significantly decrease the amount of time required to be expended during the lining of a blast hole.
Still a further object of this invention is to provide a blast hole liner sleeving stand which will releasably secure a blast hole liner and which will allow for convenient filling of a blast hole liner with bulk blasting powder.